Production of acetic anhydrid and acetaldehyde.



-1 ED STATES, PATENT ()FFICE.

JOSEPH KOETSCHET AND MAURICE BEUDET, F LYON, FRANCE, ASSIGNORS TO SOCIETE GHI'MIQUE DES USINES DU RHONE, (ANCIENNEMENT, GILLIARD, P. MONN ET ET CARTIER) OF PARIS, FRANCE.

PRODUCTION OF ACETIC ANHYDRID AND,ACETALDEHYDE.

No Drawing.

T 0' all whom it may concern:

Be it known that we, JOSEPH Kon'rsonn'r,

a citizen of the Swiss Republic, of 67 Boulevard des Belges, Lyon, France, and MAtmIcn BEUnn'r, a' citizen of the Republic of France,

of 25 Rue Bugeaud, Lyon, France, have in-.

' vented certain new and useful Improvements in or Relating to the Production of Acetic Anhydrid and Acetaldehyde, of which the following is a specification.

Ethylidene diacetate is a body which is relatively unstable under heat.

Geuther, who first prepared it (Liebz'gs Annalen Vo. 106, page 249) already observed that this body gradually decomposes and becomes acid when sub ected to repeated which form the subject of the English Patent No. 23190 of 1914 dated 17 January 1914.

In this patent the overheating is effected at temperatures between 250 and 300. As regards the catalyzers, their action is utilized at the boiling temperature of the diacetate.

Further, it is sought to accentuate this ac- 1 tion by accompanying it with a slighto'verheating, produced, 1n the apparatus employed, by the long column by which the apparatus is surmounted.

In all cases a mixture of aldehyde, anhy drid and acetic acid escapes from the reac--.--- tion vessel and has then to be separated.

The practical carrying out of this process is not unattended by drawbacks. Owing to the high temperature to which the dlacetate is subjected, sometimes in presence of powerful catalyzers, such as sulfuric acid, secondary reactions always oocur,'and-in numerous cases an intense formation of tar is observed.

Further. the catalyzer is often destroyed, and its concentration relatively to the dime- Specification of Letters Patent.

These are in fact the modes of operation Patented Mar. 25, 1919.

Application filed June 11, 1918. Serial No. 239,853.

tate increases in proportion as the operation proceeds, this latter fact being very disadvantageous in the majority of cases.

Moreover one has at the end of the operation a distillate cOllSiStiDg of a mixture of aldehyde, partly polymerized, acetic acid and acetic anhydrid. Nowwhen large quantities are dealt with, the separation of these constituents is a delicate matter, in view of the ease with whichthc anhydrid and the aldehyde recombine, especially when they are accompanied by traces of catalyzers (acids, acid salts, neutral salts of strong acids etc.)

The applicants have now found that it is possible on the one hand to effect the decom position of ethylidene diacetate'into acetaldehyde and acetic anhydrid with quantitativeyields, and on the other hand-to effect in a single operation the decomposition of the diacetate and the separation of'the two resulting products.

To obtain the first of these results, it-suffices to heat the ethylidene diacetate in pres-- ence of appropriate catalyzers, well below its boiling point; under these conditions the conversion of the ethylidene'diacetate into acetaldehyde and acetic anhydrid is effected normally without causing formation of tar or secondary reactions. To obtain, moreover, the second result, it is advisable to maintain the temperature of the reaction even belowthe boiling oint. of the acetic anhydrid: the acetalde yde then escapes alone from the reaction vessel in which the an h drid accumulates.

T e elimination of the acetaldehyde may also be assisted by entraining it by. a current of dry air.

One can naturallycarry out the decomposition of the whole of the diacetate taken, or arrest the decomposition when a fraction still remains unaltered. In this latter case,

a the anhydrid formed may be separated easily.

by rectlfication, from the remaining diacetate.

The relatively very low temperatures at which the working is effected hkewise permit, when'a very energetic catalyzer is employed. of modifying the action of the catalyzer, by diluting the ethylidene diacetate with an appropriate solvent, and in particular, with acetic acid and acetic anhydrid.

' The applicants have also found that when the catalyzer employed is soluble neither in the diacetate. nor in the anhydrid, nor in the mixture of thesetwo substances, it is very advantageous to use it in solution in a neutral body, not susceptible of distilling at the temperature at which the operation is conducted.

Example I Parts. Ethylidene dlacetate 500 Sodium p vrosu'lfatc 15 are heated in a distilling vessel at l-25 140 C. 120 to 150 parts of acetaldehyde distil over and are collected. The acetic nhydridremains in the apparatus and is purified by rectification.

The yield is approximately theoretical. Example II: One works as stated in EX- ample It with a mixture consisting of:

Parts.

Ethylidene diacetate 500 Monosodic orthophosphate 30 The reaction takes place very well at about Example III: Into 500 parts of ethylidene (liacetate contained in a distilling apparatus are run 35 parts-of finely powdered meta boric acid. While maintaining strong stirring, the mixture is heated at 110130 C.. and a small current of dry air is bubbled through the mixture. This current, suitably .cooled (.n issuing from the apparatus and then washed, deposits:

i Parts. Acetaldehyde 100 There remain in the apparatus 0 Parts. Acetic anhydrid 230 Unaltered diacetate 170 3 Example IV: Into a distilling apparatus containing:

. Parts. Ethyhdene dlacetate 250 Acetic anhydrid 100 are charged Parts. v sulfaceticacid 5 The mixture is heated at 125-135 O. and parts of aldehyde distil over.

The anhydrid which remains in the apparatus is not contaminated with tar.

Example V: Int-he following example the use of a neutral solvent for the catalyzer is combined with the employmentof a catalyzer which is insoluble in the diacetate or in the anhydrid; 5 parts of metaboric acid are dissolved hot in 100 parts of a heavypetroleum having a boiling point at from 200 to 250 C. Into this solution are poured 500 parts of ethylidene diacetate whereupon the solution is heated without agitating up to a temperature of from 100"to 130 '0. Results are thereby obtained analogous to those indicated above in connection with Example III. p I

What we claim as our invention, and desire to secure by Letters Patent, is

1. A process of making acetaldehyde and acetic anhydrid, comprising heating ethylidene diacetate in presence of a catalyzer while maintaining the temperature below the boiling point of the ethylidene diacetate. 2. A process of making acetalydehyde and acetic anhydrid, comprising heating ethylidene diacetate in presence of a catalyzer while maintaining the temperature below the boiling point of acetic anhydrid and above that of the acetaldehyde, whereby the decomposition of the ethylidene diacetate and separation of acetaldehyde from acetic anhydrid are eflected simultaneously.

3. A process of making acetaldehyde and acetic anhydrid, comprising heating ethylidene diacetate in presence of a catalyzer while maintaining the temperature below the boiling point of acetic anhydrid and aboie tion of the catalyzer, while maintaining the temperature below the boiling point of acetic anhydrid and above that of acetaldehyde.

6. A process of making acetaldehyde and acetic anhydrid,comprising heating ethylidene diacetate in presence of a catalyzer dis solved in a solvent indifi'erent to the'reaction, while maintaining the temperature below the boiling point of the ethylidene diacetate.

7. A process of making acetaldehyde and acetic anhydrid, comprising heating ethylidene diacetate in presence of a catalyzer dissolved in asolvent indifferent to the reaction while inaintaining the temperature below the boiling point of acetic anhydrid and above that of acetaldehyde.

whereof we have signedour In testimony names. to this specification.

JOSEPH KOETSCHET. MAURICE BEUDET.

In the presence of- GRADY Comma, MARIN VACHON. 

